Enthusiastt vs engineer

Hi all
Performance logs in the RPS magazine show Eurostar losing speed on major climbs such as from the Medway Tunnel to the North Downs Tunnel. Yet on a rail forum a Eurostar engineer insists Eurostars can maintain maximum speed on all gradients and even accelerate up some. He claims as an engineer he knows better than amateurs timing trains as he does cab rides. Who is correct?

daveb0789 said:

Hi all
Performance logs in the RPS magazine show Eurostar losing speed on major climbs such as from the Medway Tunnel to the North Downs Tunnel. Yet on a rail forum a Eurostar engineer insists Eurostars can maintain maximum speed on all gradients and even accelerate up some. He claims as an engineer he knows better than amateurs timing trains as he does cab rides. Who is correct?

The enthusiast reports what they observe. That can depend on, for example, both the train capability and the driving technique. The driver may push the train up to its maximum performance if there is a Eurostar engineer in the cab who wants to observe how fast it can go. But, if the driver is unaware that the train is being timed, he (or she) may just drive in a mode that keeps to schedule, or that tries to conserve "energy".

Bevan Price

I agree strongly with the general point made by Bevan, but with the Eurostars think that technical performance considerations also come into play in that I do not believe that they are able to maintain their full operating speed on appreciable adverse gradients.
The Tractive Effort at 300kph (from SNCF curve in test report accessed by Ref 2 of Wikipedia Class 373 entry)= 146kN.
The set resistance at 300kph (from speed run-down resistance curve plotted in Rochard & Schmid, Proc IME (Part F) Vol 214 Page 193) = 123kn.
Using Gradient Force (kN) = Mass (tonnes)*g /Grad
(where g=9.81m/s^2 and Grad is the gradient expressed as 1:Grad), then the 'balancing gradient' for an assumed typical 800t gross weight Eurostar is 1:341, and on gradients steeper than this line speed would not be able to be reached/maintained.
The climb after the Medway viaduct up to North Downs Tunnel is at a prevailing gradient of 1:41. The balancing speed of a Eurostar on such a gradient is only around 170kph, but over the relatively short distance of about 1.55 miles the running speed would only be expected to fall away below the line speed by perhaps 20kph.

David Stannard


9102 said:

daveb0789 said:

Hi all
Performance logs in the RPS magazine show Eurostar losing speed on major climbs such as from the Medway Tunnel to the North Downs Tunnel. Yet on a rail forum a Eurostar engineer insists Eurostars can maintain maximum speed on all gradients and even accelerate up some. He claims as an engineer he knows better than amateurs timing trains as he does cab rides. Who is correct?

The enthusiast reports what they observe. That can depend on, for example, both the train capability and the driving technique. The driver may push the train up to its maximum performance if there is a Eurostar engineer in the cab who wants to observe how fast it can go. But, if the driver is unaware that the train is being timed, he (or she) may just drive in a mode that keeps to schedule, or that tries to conserve "energy".

Bevan Price

That's a fantastic answer. Thank you very much. I understand your points Bevan both from a railway performance enthusiasts point of view and as a qualified train driver myself.


dstannard said:

I agree strongly with the general point made by Bevan, but with the Eurostars think that technical performance considerations also come into play in that I do not believe that they are able to maintain their full operating speed on appreciable adverse gradients.
The Tractive Effort at 300kph (from SNCF curve in test report accessed by Ref 2 of Wikipedia Class 373 entry)= 146kN.
The set resistance at 300kph (from speed run-down resistance curve plotted in Rochard & Schmid, Proc IME (Part F) Vol 214 Page 193) = 123kn.
Using Gradient Force (kN) = Mass (tonnes)*g /Grad
(where g=9.81m/s^2 and Grad is the gradient expressed as 1:Grad), then the 'balancing gradient' for an assumed typical 800t gross weight Eurostar is 1:341, and on gradients steeper than this line speed would not be able to be reached/maintained.
The climb after the Medway viaduct up to North Downs Tunnel is at a prevailing gradient of 1:41. The balancing speed of a Eurostar on such a gradient is only around 170kph, but over the relatively short distance of about 1.55 miles the running speed would only be expected to fall away below the line speed by perhaps 20kph.

David Stannard


9102 said:

daveb0789 said:

Hi all
Performance logs in the RPS magazine show Eurostar losing speed on major climbs such as from the Medway Tunnel to the North Downs Tunnel. Yet on a rail forum a Eurostar engineer insists Eurostars can maintain maximum speed on all gradients and even accelerate up some. He claims as an engineer he knows better than amateurs timing trains as he does cab rides. Who is correct?

The enthusiast reports what they observe. That can depend on, for example, both the train capability and the driving technique. The driver may push the train up to its maximum performance if there is a Eurostar engineer in the cab who wants to observe how fast it can go. But, if the driver is unaware that the train is being timed, he (or she) may just drive in a mode that keeps to schedule, or that tries to conserve "energy".

Bevan Price

On three class 395 runs I have seen variable falls in speed from Medway viaduct south to the north portal of North Downs tunnel - 223 to 205, 222 (max in dip 226) to 207 and 211 (216 in dip) to 200. On my last Eurostar run it was, from an Ebbsfleet start, 261 (263 in dip) to 253. The one before that, again an Ebbsfleet start, 266 (271 in dip) to 258.

daveb0789 said:

That's a fantastic answer. Thank you very much. I understand your points Bevan both from a railway performance enthusiasts point of view and as a qualified train driver myself.


dstannard said:

I agree strongly with the general point made by Bevan, but with the Eurostars think that technical performance considerations also come into play in that I do not believe that they are able to maintain their full operating speed on appreciable adverse gradients.
The Tractive Effort at 300kph (from SNCF curve in test report accessed by Ref 2 of Wikipedia Class 373 entry)= 146kN.
The set resistance at 300kph (from speed run-down resistance curve plotted in Rochard & Schmid, Proc IME (Part F) Vol 214 Page 193) = 123kn.
Using Gradient Force (kN) = Mass (tonnes)*g /Grad
(where g=9.81m/s^2 and Grad is the gradient expressed as 1:Grad), then the 'balancing gradient' for an assumed typical 800t gross weight Eurostar is 1:341, and on gradients steeper than this line speed would not be able to be reached/maintained.
The climb after the Medway viaduct up to North Downs Tunnel is at a prevailing gradient of 1:41. The balancing speed of a Eurostar on such a gradient is only around 170kph, but over the relatively short distance of about 1.55 miles the running speed would only be expected to fall away below the line speed by perhaps 20kph.

David Stannard


9102 said:

daveb0789 said:

Hi all
Performance logs in the RPS magazine show Eurostar losing speed on major climbs such as from the Medway Tunnel to the North Downs Tunnel. Yet on a rail forum a Eurostar engineer insists Eurostars can maintain maximum speed on all gradients and even accelerate up some. He claims as an engineer he knows better than amateurs timing trains as he does cab rides. Who is correct?

The enthusiast reports what they observe. That can depend on, for example, both the train capability and the driving technique. The driver may push the train up to its maximum performance if there is a Eurostar engineer in the cab who wants to observe how fast it can go. But, if the driver is unaware that the train is being timed, he (or she) may just drive in a mode that keeps to schedule, or that tries to conserve "energy".

Bevan Price

Fastest Times Editor